AsRock B550M ITX\ac PCIE x16 mode causes stutters

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   Hello everyone!

I Own AsRock B550M ITX\ac and (AsRock B520M ITX\a) almost identical boards that have identical problem.

Specs:

PC #1
AsRock B550M ITX\a
Ryzen 5700G
Adata XPG Spectrix D41 2x16gb 3600mhz
Samsung Evo 980 1Tb m.2 SSD
Colorful RTX3070 Vulcan

PC #2
AsRock B520M ITX\a
Ryzen 5600G
Netac RGB 2x8gb 3200mhz
Samsung Evo 980 1Tb m.2 SSD
Asus Turbo GTX1080

Both have latest Stable BIOS from website.

When in BIOS PCI mode is set to x16 + Auto (This is important)

So the problem with PC #2 - severe wireless mouse stutter. Works fine only when it is less then 50cm away. More than this distance - severe stuttering of cursor.

So the problem with PC #1 - External audio interface M-Audio AIR 192\6 - constant static heard. When GPU is under LOAD like move rendering in Topaz Video AI - severe system stutter - mouse stutters freezes, keyboard samem Windows 10 also stutters.
Also if i connect Mouse and keyboard via dongle in 1 USB slot with usb2.0 1 to 3 ports splitter - they stutter even without GPU in standby mode. Connectiong Keyboard via usb cable - makes its backlight blink like there is not enough power given.

NOW ATTENTION!

If in bios i set PCI mode is set to x8x8 + Auto
Both PC worrk TOTALY fine! Not stuttering no static in External Audio. Keyboard and mouse work though usb splitter perfectly.

If I set PC #1 to PCI x16+Gen3 = works fine bo mouse stutter

If I set PC #2 to PCI x16+Gen3 = No mouse and system stutter. But still get Static in External audio + issues with keyboard and mouse connected with USB splitter

I use USB splitter because there is not enough usb ports for all devices.

So What is this thing With PCIE in x16 and x8x8 Mode making my PC work bad or good? 

I need my GPU to be connected via x16 mode it gives me more rendering power than when it is in x8x8 mode.

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BoostOrDie Members Profile Send Private Message Find Members Posts Add to Buddy List Newbie Joined: 11 Mar 2025 Status: Offline Points: 35	Post Options Post Reply Quote BoostOrDie Report Post Thanks(0) Quote Reply Topic: AsRock B550M ITX\ac PCIE x16 mode causes stutters Posted: 11 Mar 2025 at 6:53am
	Hello everyone! I Own AsRock B550M ITX\ac and (AsRock B520M ITX\a) almost identical boards that have identical problem. Specs: PC #1 AsRock B550M ITX\a Ryzen 5700G Adata XPG Spectrix D41 2x16gb 3600mhz Samsung Evo 980 1Tb m.2 SSD Colorful RTX3070 Vulcan PC #2 AsRock B520M ITX\a Ryzen 5600G Netac RGB 2x8gb 3200mhz Samsung Evo 980 1Tb m.2 SSD Asus Turbo GTX1080 Both have latest Stable BIOS from website. When in BIOS PCI mode is set to x16 + Auto (This is important) So the problem with PC #2 - severe wireless mouse stutter. Works fine only when it is less then 50cm away. More than this distance - severe stuttering of cursor. So the problem with PC #1 - External audio interface M-Audio AIR 192\6 - constant static heard. When GPU is under LOAD like move rendering in Topaz Video AI - severe system stutter - mouse stutters freezes, keyboard samem Windows 10 also stutters. Also if i connect Mouse and keyboard via dongle in 1 USB slot with usb2.0 1 to 3 ports splitter - they stutter even without GPU in standby mode. Connectiong Keyboard via usb cable - makes its backlight blink like there is not enough power given. NOW ATTENTION! If in bios i set PCI mode is set to x8x8 + Auto Both PC worrk TOTALY fine! Not stuttering no static in External Audio. Keyboard and mouse work though usb splitter perfectly. If I set PC #1 to PCI x16+Gen3 = works fine bo mouse stutter If I set PC #2 to PCI x16+Gen3 = No mouse and system stutter. But still get Static in External audio + issues with keyboard and mouse connected with USB splitter I use USB splitter because there is not enough usb ports for all devices. So What is this thing With PCIE in x16 and x8x8 Mode making my PC work bad or good? I need my GPU to be connected via x16 mode it gives me more rendering power than when it is in x8x8 mode.

BoostOrDie Members Profile Send Private Message Find Members Posts Add to Buddy List Newbie Joined: 11 Mar 2025 Status: Offline Points: 35	Post Options Post Reply Quote BoostOrDie Report Post Thanks(0) Quote Reply Posted: 6 hours 31 minutes ago at 4:14pm
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Xaltar Members Profile Send Private Message Find Members Posts Add to Buddy List Moderator Group Joined: 16 May 2015 Location: Europe Status: Offline Points: 29638	Post Options Post Reply Quote Xaltar Report Post Thanks(0) Quote Reply Posted: 6 hours 12 minutes ago at 4:33pm
	If you haven't already, I would open a support ticket with ASRock. This is a community forum and while ASRock does check in here quite often they don't reply every thread. Have you benchmarked the difference between x8 and x16 on your system? The reason I ask is because it often doesn't make a difference. In a lot of cases the GPU isn't able to fully saturate x8 so there isn't a performance hit. In addition the saturation will vary depending on the type of load. One game for example may fully saturate your PCIe bandwidth but another won't even come close.